Reverse osmosis apparatus and method for making same

ABSTRACT

Reverse osmosis apparatus comprises one or a plurality of reverse osmosis membrane tubes enclosed within a housing. Each tube comprises two mating rigid support forms, each having a long and narrow perforate channel therein and flat flanges extending laterally therefrom on opposite sides of the channel. Two reverse osmosis membrance sheets are clamped between the flanges, and each sheet extends into one of the channels, so that together the sheets form a tube for conducting solution. Elements of the housing can bear on the flanges with clamping pressure. A series of such tubes can be formed side-by-side in a unit. The apparatus advantageously is made by placing a flat sheet of membrane across each of first and second support forms, with or without an interposed spacer sheet, depressing the membrance into the channel by a mandrel or by applying a gas pressure differential, and then fitting the two together with the channels facing toward one another and in register. The flanges are then clamped together and the whole is enclosed in a housing in spaced relation thereto for collecting solvents. Each support form can have a series of such channels spaced from and parallel to one another.

United States Patent Brown et al. I

[54] REVERSE OSMOSIS APPARATUS AND METHOD FOR MAKING SAME [72]Inventors: Barry M. Brown, Rochester; Elbert L. Ray, Penfield, both ofNY.

3,616,926 11/1971 Lichtenstein ..210/321 Primary Examiner-Frank A.Spear, Jr.

AttorneyWilliam T. French, Robert F. Crocker and Henry M. Chapin [451Oct. 31, 1972 [5 7 1 ABSTRACT Reverse osmosis apparatus comprises one ora plurality of reverse osmosis membranetubes enclosed within a housing.Each tube comprises two mating rigid support forms, each having a longand narrow perforate channel therein and flat flanges extendinglaterally therefrom on opposite sides of the channel. Two reverseosmosis membrance sheets are clamped between the flanges, and each sheetextends into one of the channels, so that together the sheets form atube for conducting solution. Elements of the housing can bear on theflanges with clamping pressure. A series of such tubes can be formedside-by-side in a unit. The apparatus advantageously is made by placinga flat'sheet of membrane across each of first and second support forms,with or without an interposed spacer sheet, depressing the membranceinto the channel by a mandrel or by applying a gas pressuredifferential,

and then fitting the two together with the channels facing toward oneanother and in. register. The flanges are then clamped together and thewhole is enclosed in a housing in spaced relation thereto for collectingsolvents. Each support form can have a series of such channels spacedfrom and parallel to one another.

14 Claims, 6 Drawing Figures PATENTEDIIBICH I912 3.701.431

' SHEET 1 BF 2 BARRY M. BROWN ELBERT L. RAY INVENTORS ATTORNEY 1. Fieldof the Invention The present invention relates to a novel reverseosmosis apparatus, and a novel method for making such apparatus.

2. The Prior Art Reverse osmosis membranes such as the cellulose estermembranes described in U.S. Pats. Nos. 3,522,335 and 3,527,853 have beenknown for some time as semipermeable membranes for separating solventsfrom solutions. Such membranes comprise a thin skin or active surface onone side thereof which is porous to the passage of water or othersolvent, but not to the salt or other solute in the solution. Forexample, the separation of practically pure water froma solutioncontaining salt or. other solute has been accomplished by passing theimpure solution through a tube formed of such a membrane; andconversely, the solution becomes more concentrated, which is sometimesthe main objective. Such tubes have been found to be quite satisfactorybecause of their low cost, easy mechanical cleaning, and goodsurface-volume ratio; and also because they allow turbulent andunrestricted flow. Unfortunately, such tubes have been difficult toform, and to insert in the final apparatus assembly.

SUMMARY OF THE INVENTION .of multiple tubes. Generally speaking, themethod comprises providing first and second identical rigid supportforms, each of which has a relatively long and narrow perforated channeltherein, and flat flanges extending laterally therefrom on oppositesides of the channel. The flanges and the channels 'of the two supportforms are so constructed and arranged as to register with one another,with the channels facing toward one another.

Two reverse osmosis membrane sheets are positioned between the supportforms in contact with their respective flanges and are depressed intotheir respective channels. Then the flanges are clamped tightlytogether, and the support forms and .the resulting reverse osmosismembrane tube are enclosed in a housing in spaced relation thereto toprovide space for collecting solvent which passes from the interior ofthe tube to the exterior.

- The membrane sheets can be depressed into the respective channels byemploying one or more removable mandrels or-shafts of a material such aswood or plastic; or a gas pressure differential may be employed to forcethe membrane material into the channels.

A plurality of similarly formed tubes can be positioned within thehousing, and can be operated individually, or can be connected togetherin series so that solution can be forced into'an initial tube, thenthrough one or more other tubes in series therewith, and discharged froma final tube.

The resulting reverse osmosis apparatus assembly is also part of thepresent invention and will be described in more detail hereinafter.

THE DRAWING The principles of the invention will be describedhereinafter with reference to the drawing, wherein:

FIG. 1 is a fragmentary exploded perspective view showing elements ofone-half of a reverse osmosis module in position to be assembled;

FIG. 2 is across-sectional view of the half module 2 after assembly,taken along the line 2--2 in FIG. 1;

dispensed with when perforate support form 11 is con- FIG. 3 is avertical sectional view of reverse osmosis apparatus assembled forseparating solvent from a solution, taken along the line 3 -3 in FIG. 4;

FIG. 4 is a vertical sectional view, partly in .side

elevation, of the assembled apparatus taken along theline 4-4 in FIG. 3;

FIG. 5 is an end elevational view of a modified form of a shaft elementfor forming two tubular membranes; and

FIG. 6 is a schematic end elevational view, partly inv phantom, showingan arrangement of elements for forming tubular membranes bypressuredifferential.

THE PREFERRED EMBODIMENT concave channels 13 and 15 therein, and flatflanges l7, l9, and 21 extending laterally therefrom on opposite sidesof the channels. Each channel has a plurality of holes 23 and 25penetrating therethrough so that the channels are perforate for the flowof solvent therefrom. Support form 11 can be constructed of any materialstrong enough to withstand high pressures; for example, a syntheticresin such as polystyrene, fiberglass bonded with epoxy resin, or ametal.

A flat spacer sheet 29 of porus flexible material, such as cotton ornylon cloth, or woveni fiberglass, is adapted to be positioned on theflanges, and a flat flexible semipermeable reverseosmosis membrane sheet31 is adapted to be positioned on top of the spacer sheet with itsactive surface concave so as to be on the inside of the finished tube.Both sheets can be depressed together into the channels 13 and 15 byapplying generally semi-cylindrical mandrel or shaft members 32 and 33thereto, forming an assembled half unit 34 as shown in FIG. 2. Spacersheet 29 is optional for conducting liquid to the perforations 23 and25, and can be structed of a porous material, such as sintered metalpowder. To assure that undue stretching or rupture of the membrane sheetdoes not occur, the technician should avoid applying excessive force,for example, by applying the mandrels one at a time, and/or pressing themembrane into the channels by hand gently.

A second identical half unit 36 is made up in the same way, and ispositioned on top of the first half unit 34 with the flanges andchannels in register with one another, and with the concave channelsfacing toward one another so as to create a tube. Adhesive material maybe applied to the juxtaposed flat areas of the membranes to preventcross leakage when in use.

Now referring to FIG. 3, the assembled full unit dinal blocks of metal,plastic, or other firm material 37 its own set of bottom blocks 41 andthe blocks 39. The

assembly is completed by top and bottom plates 43 and 45 which bearagainst the adjacent blocks and are held tightly thereagainst by bolts47 or other means, such as an hydraulic press. Shafts 32 and 32 are thenwithdrawn lengthwise from each unit, leaving tubes 46 for receivingsolution.

It will be seen that the resulting reverse osmosis membrane tubes 46 areenclosed within a housing which is spaced therefrom to form open spaces51, 53, and 55 for the accumulation of solvent which passes through themembranes when a solution is pumped through the tubes.

As shown in FIG. 4, the ends of the housing can be covered with suitableend plates 59 and 61 which are bolted at their peripheries to the topand bottom members 43 and 45, and have apertures therethrough to receiveprotruding ends of the membrane tubes 46 which project a short distancetherefrom and are turned out against the outer surfaces of the endplates to which they may be cemented with a suitable adhesive, ifdesired. The protruding ends of the tubes 46 are clamped fluid tightlyagainst the outside surfaces of the end sheets by flanges 63, 65, 67,and 69 on the ends of conduits- 71, 73, and 75 for conducting thesolution from whichsolvent is to be extracted. In the modificationshown, solution is pumped in through conduit 71 at high pressure, passesthrough a first membrane tube 46, and then through a return bend 73 andinto the second membrane tube 46 from which it leaves through conduit75. Solvent which passes through membrane tubes 46 enters spaces 51, 53,and 55 from which it is removed through valve-controlled conduits, 85,87, and 89.

Instead of the precise arrangement shown in FIG. 4, the apparatus can beoperated with each membrane tube 46 having an individual entrance andexit for solution; or a series of more than two membrane tubes can beconnected together in series by return bends.

Referring to FIG. 5, instead of employing the individual half shafts 31and 33 as shown in FIG. 1, they can be combined into a single unitaryassembly 91. This assembly, of course, must be withdrawn beforesufficient clamping force has been applied to capture the assembly.

Also, it is evident that instead of using half shafts as shown in FIG.1, each shaft can be generally cylindrical in shape and positioned onthe top of the membrane 31 to press the membrane and spacer into thechannels. Then the membrane and spacer of the other half unit can belaid across the protruding tops of the cylindrical shafts, after which asecond half support form can be brought down into register with thefirst half.

FIG. 6 shows how suction may be employed to shape the membrane. Asupport form 11' is positioned on the periphery of a vacuum box 93, withthe membrane 31' and spacer 29' lying across the top of the support.Upon the application of a vacuum to conduit 94, the sheets are suckeddown into the channels 13 and 15'. Conversely, the necessary pressuredifferential can be developed by positioning box 93 on the top ofmembrane 31 and applying air at superatmospheric pressure throughconduit 94.

The invention has been described in detail with particular reference topreferred embodiments thereof,

' but it will be understood that variations and modifications can beeffected within the spirit and scope of the invention.

We claim:

l. A method for making reverse osmosis apparatus comprising a reverseosmosis membrane tube for carrying a stream of solution, and spaceoutside of said tube for collecting solvent which penetrates saidmembrane,

said method comprising:

providing first and second rigid support forms, each having a relativelylong and narrow perforate channel therein and flat flanges extendinglaterally therefrom on opposite sides of said channel, the flanges andthe channels of said first and second forms being adapted to registerwith one another with said channels facing toward one another;positioning two reverse osmosis membrane sheets between said supportforms in contact with the respective flanges thereof and depressed intothe respective channels thereof, and with the active surfaces thereoffacing toward one another; clamping said flanges tightly together; andenclosing said support forms and the resulting reverse osmosis membranetube in a housing in spaced relation thereto for collecting suchsolvent. 2. A method in accordance with claim 1 wherein each membranesheet is depressed into its channel by said channel, and entering saidshaft into said channel;

' said method also comprising withdrawing said shaft means through theend of the resulting tube after clamping said flanges together.

3. A method in accordance with claim 2 wherein a separate generallysemi-cylindrical shaft is entered into each channel while said supportforms are out of register, and wherein said support forms are thenbrought into register with one another.

4. A method in accordance with claim 2 wherein said shaft means isgenerally a cylinder, said method also comprising placing said cylinderon a first one of said sheets and depressing said first sheet into thechannel of said first support form; placing a second one of said sheetson top of said cylinder; and then placing said second support form onsaid second sheet in register with said first support form.

5. A method in accordance with claim 1 wherein each membrane isdepressed into its channel by applying suction to the side of saidsupport form opposite said membrane.

6. A method in accordance with claim 1, also comprising interposingbetween each reverse osmosis sheet and the adjacent support form aspacer sheet of porous flexible material, said sheets also beingdepressed into said channels.

7. A method in accordance with claim 1 wherein said first and secondrigid support forms are provided with a plurality of said channels inspaced parallel relationship and a series of said reverse osmosismembrane tubes are thus formed; said method also comprising stacking aplurality of said series of tubes in said housing.

8. Reverse osmosis apparatus comprising two rigid support forms, eachhaving a relatively long and narrow perforate channel therein and flatflanges extending laterally therefrom on opposite sides of said channel,said channels and said flanges beingin register;

two reverse osmosis membrane sheets clamped between the flanges of saidsupport forms, each sheet extending into one of said channels andforming together a reverse osmosis tube for conducting a solution, theactive surface of each such membrane being on the. inside of said tube;

and a housing enclosing said support forms in spaced relation theretofor collecting solvent which penetrates the wall of said tube.

9. Reverse osmosis apparatus in accordance with claim 8 also comprisingspacer sheets of porous flexible material interposed between eachsupport sheet and the adjacent membrane.

10. Apparatus in accordance with claim 8 comprising a plurality of saidtubes within said housing; means for supplying solution to and removingsolution from said tubes; and means for removing solvent from the spacein said housing outside of said tubes.

11. Apparatus in accordance with claim 8, also comprising means forsupplying solution to an initial one of said tubes, means connecting aplurality of said tubes together end-to-end in series relationship; andmeans for removing solution from the final one of said tubes in saidseries.

12. Apparatus in accordance with claim 8 wherein said housing comprisesa plurality of blocks in clamping contact with said flanges.

13. A tubular assembly for reverse osmosis apparatus, said assemblycomprising two rigid support forms, each having a relatively long andnarrow perforate channel therein and flat flanges extending laterallytherefrom on opposite sides of said channel, said channels and saidflanges being in register; and

two reverse osmosis membrane sheets clamped between the flanges of saidsupport forms, each sheet extending into one of said channels andforming together a reverse osmosis tube for conducting a solution, theactive surface of each such membrane being on the inside of said tube.

14. A tubular assembly in accordance with claim 13, also comprisingspacer sheets of porous flexible material interposed between eachsupport sheet and the adjacent membrane.

1. A method for making reverse osmosis apparatus comprising a reverseosmosis membrane tube for carrying a stream of solution, and spaceoutside of said tube for collecting solvent which penetraTes saidmembrane, said method comprising: providing first and second rigidsupport forms, each having a relatively long and narrow perforatechannel therein and flat flanges extending laterally therefrom onopposite sides of said channel, the flanges and the channels of saidfirst and second forms being adapted to register with one another withsaid channels facing toward one another; positioning two reverse osmosismembrane sheets between said support forms in contact with therespective flanges thereof and depressed into the respective channelsthereof, and with the active surfaces thereof facing toward one another;clamping said flanges tightly together; and enclosing said support formsand the resulting reverse osmosis membrane tube in a housing in spacedrelation thereto for collecting such solvent.
 2. A method in accordancewith claim 1 wherein each membrane sheet is depressed into its channelby placing shaft means on the surface thereof opposite said channel, andentering said shaft into said channel; said method also comprisingwithdrawing said shaft means through the end of the resulting tube afterclamping said flanges together.
 3. A method in accordance with claim 2wherein a separate generally semi-cylindrical shaft is entered into eachchannel while said support forms are out of register, and wherein saidsupport forms are then brought into register with one another.
 4. Amethod in accordance with claim 2 wherein said shaft means is generallya cylinder, said method also comprising placing said cylinder on a firstone of said sheets and depressing said first sheet into the channel ofsaid first support form; placing a second one of said sheets on top ofsaid cylinder; and then placing said second support form on said secondsheet in register with said first support form.
 5. A method inaccordance with claim 1 wherein each membrane is depressed into itschannel by applying suction to the side of said support form oppositesaid membrane.
 6. A method in accordance with claim 1, also comprisinginterposing between each reverse osmosis sheet and the adjacent supportform a spacer sheet of porous flexible material, said sheets also beingdepressed into said channels.
 7. A method in accordance with claim 1wherein said first and second rigid support forms are provided with aplurality of said channels in spaced parallel relationship and a seriesof said reverse osmosis membrane tubes are thus formed; said method alsocomprising stacking a plurality of said series of tubes in said housing.8. Reverse osmosis apparatus comprising two rigid support forms, eachhaving a relatively long and narrow perforate channel therein and flatflanges extending laterally therefrom on opposite sides of said channel,said channels and said flanges being in register; two reverse osmosismembrane sheets clamped between the flanges of said support forms, eachsheet extending into one of said channels and forming together a reverseosmosis tube for conducting a solution, the active surface of each suchmembrane being on the inside of said tube; and a housing enclosing saidsupport forms in spaced relation thereto for collecting solvent whichpenetrates the wall of said tube.
 9. Reverse osmosis apparatus inaccordance with claim 8 also comprising spacer sheets of porous flexiblematerial interposed between each support sheet and the adjacentmembrane.
 10. Apparatus in accordance with claim 8 comprising aplurality of said tubes within said housing; means for supplyingsolution to and removing solution from said tubes; and means forremoving solvent from the space in said housing outside of said tubes.11. Apparatus in accordance with claim 8, also comprising means forsupplying solution to an initial one of said tubes, means connecting aplurality of said tubes together end-to-end in series relationship; andmeans for removing solution from the final one of said tubes in saidseries.
 12. Apparatus in accordance with claim 8 wherein sAid housingcomprises a plurality of blocks in clamping contact with said flanges.13. A tubular assembly for reverse osmosis apparatus, said assemblycomprising two rigid support forms, each having a relatively long andnarrow perforate channel therein and flat flanges extending laterallytherefrom on opposite sides of said channel, said channels and saidflanges being in register; and two reverse osmosis membrane sheetsclamped between the flanges of said support forms, each sheet extendinginto one of said channels and forming together a reverse osmosis tubefor conducting a solution, the active surface of each such membranebeing on the inside of said tube.
 14. A tubular assembly in accordancewith claim 13, also comprising spacer sheets of porous flexible materialinterposed between each support sheet and the adjacent membrane.